IV bags contain saline and/or glucose solution for continuous intravenous injection. It is often desired to administer other medication, drugs or drug combinations, at the same time, and IV bags are provided for this purpose with a formation including a seal through which such medication can be injected from a syringe through a needle that penetrates the seal, which is capable of self-sealing, possibly numerous times, after the needle is removed.
Needle stick injuries are a problem that has been addressed in many ways, often by using a retraction mechanism that retracts the needle into a shield or sheath after use to inject a patient.
An arrangement involving a guard that essentially permanently encloses the needle was proposed in WO 2000/013727 for the reverse operation, namely drawing medicament into a syringe from a vial prior to injecting the patient. Here, there was concern about risks in changing needles after filling the syringe. The arrangement had an injecting needle surrounded by a sheath used to penetrate the vial seal, both surrounded by a guard attached by a frangible connection, the points of both needles being within the guard so as to be inaccessible to human fingers. Breaking off the guard and sheath gives access to the needle, which can then be used for the injection.
WO03/051430 discloses a needle stick injury prevention arrangement specifically for use with IV bags, in which the needle is enclosed within an open-ended shield, its point some distance inside the open end. This is possible, as the IV bag has a tailed injection arrangement, in which the seal is at the end of a tube, and the point of the needle of the syringe can be concealed well within the shield, yet be able to penetrate the seal while the shield is advanced up the tube. The point is still concealed when the cannula is withdrawn together with the shield.
Problems were encountered with this arrangement, however, particularly in regard to the connection of the needle to the shield. The attachment methods described in WO03/051430 include adhesive or solvent welding, for permanent attachment, or, for fitting at time of use, an interference fit or a click fit. Adhesive or solvent welding have proved problematic in manufacture, while interference, screw and click fit connections have failed in use, with attendant risk of needle stick injury, even enhanced risk on account of the failure mode.